Small molecule organic electroluminescence device (OLED) and Polymer organic electroluminescence device (PLED) have the advantages of active light-emitting, high brightness, full-color display, low driving voltage, low device thickness, flexible display ability, and simpler manufacturing process as compared to the liquid crystal display (LCD) device and plasma display device (PDP), and the like, and have a promising application in large screen flat panel displays and flexible displays.
According to the differences in the organic film materials of the carrier transport layer and the light-emitting layer used in the components, the organic electroluminescence device can be divided into two different classes. One is small molecule-based organic LEDs, briefly OLEDs, which use organic dyes and pigments as the light-emitting materials, wherein a reprehensive example of small molecule light-emitting material is Alq (8-hydroxyquinoline aluminum). The other is polymer-based LEDs, briefly PLED, which use conjugated polymers as the light-emitting materials, wherein a reprehensive example of polymer light-emitting material is PPV (polyphenylene vinylene and derivatives thereof). Organic electroluminescence device is a current type semiconductor light-emitting device based on an organic material. Its structure is typically obtained by forming a light-emitting layer made of an organic light-emitting material with a thickness of some dozens of nanometers on an ITO glass, followed by disposing a layer of low work function metal electrode above the light-emitting layer. When a voltage is applied to the electrode, light radiation occurs in the light-emitting layer.
The organic light-emitting materials in OLED/PLED are very sensitive to water vapor and oxygen gas, and very small amount of water vapor and oxygen gas can damage the organic light-emitting materials and make the light-emitting performance of the device deteriorate. Therefore, it is a very important issue to be solved in the encapsulation of organic electroluminescence device how to reduce the permeation of water vapor and oxygen gas into the encapsulating material of the device and eliminate the water vapor and oxygen gas inside the device. In order to ensure that the device has a service life satisfactory for commercial applications, the permeation rate of the water vapor and oxygen gas into the encapsulated structure and materials of the device should be lower than 10−6 g/m2/day.
The structure of a bottom emission rigid OLED/PLED device which is conventionally encapsulated is shown in FIG. 1. An organic layer 11 and a metal electrode 12 are vapor deposited onto an ITO glass 9, respectively, and an encapsulating cover 14 attached with a drying slide 13 and a frame sealant 10 is encapsulated onto the ITO glass 9. The organic layer 11 is the light-emitting functional layer which has a structure as shown in FIG. 2, and it may comprise a hole injection layer (HIL) 3, a hole transporting layer (HTL) 4, an organic light-emitting layer (EML) 5, an electron transporting layer (ETL) 6, and an electron injection layer (EIL) 7.
The conventional encapsulating process has such disadvantages as complicated operational procedure, long curing time and high cost, and the like Moreover, because the drying slide 13 is not transparent, the conventional encapsulating process is only applicable to OLED bottom emission devices but not applicable to top emission devices.